A coolant compressor used in an air conditioner for an automobile is provided as an attachment to the automobile engine and, in use, is placed under harsh conditions in terms of vibration, heat and water. Accordingly, the thermoswitch provided to such coolant compressor for the prevention of overheating is also exposed to the same conditions as said compressor.
A typical example of the conventional thermoswitches of this type is disclosed in Japanese Utility Model Application Laid-Open No. 150245/83. In this example, electrode terminals 16a, 16b are secured to a sealing plate 17 and also project out through a resin layer 25, so that water tends to adhere to such terminals and also gaps might be produced due to vibrations transmitted to the terminals through lead wires, not shown, or for other causes to allow intrusion of water into the inside mechanism along electrode terminals 16a, 16b to wet the electrode plates and/or other elements, causing issuance of erroneous signals. Further, this conventional device had the problem of possible breakage of lead wires due to vibrations or other causes, though no mention is made of lead wires in said application.